Reticle



March 2, 1948. N. B. MEARS ET A1. 2,437,228

RETIGLE Original Filed Aug. 5, 1943 2 Sheets-Sheet l March 2, 1948. N. B. MAs ET AL 2,437,228

RETICLE Oigial Filed Aug. 5, 1943 2 Sheets-Sheet 2 negatives. ing the peripheries of the reticles are indicated body Iii and a minute central perforation I2. This design has transparent lines the width of which are equal to approximately 1/1000 of an inch. The ends of the arcuate segments II areV separated by laments of metal which support the circular center portion.

The larger reticle shown in Figs. 3 and 4 comprises a concavo-convex disk I3 formed with transparent lines I 4 some of which are disposed radially and others having arcuate segments disposed in concentric circles around a minute central perforation I5. The arcuate line segments are separated from the radial lines by filament-s of metal and similar iilaments interrupt the inner circle of the design to support the central portion of the reticle. The disk I3 isofvuniform thickness, preferably equal to about tViolin of an inch, Y j

and the width of the lines of the design may be as fine as desired with a lower limit of approximately 1/iuoo of an inch. It will be 'understood that reticles of numerous other shapes, thicknesses and sizes and with a great variety of designs may be provided within the spirit of our invention. V

According to our preferred procedure, pure copper sheets of convenient size for handling (approximately eighteen inches square, for example) and vof uniform thickness equal to that of the reticles required are burnished to give them clean, ne-toothed surfaces and are then coated on both faces with a light-sensitive enamel. Either a cold top or hot top enamel may be employed. A suitable cold top enamel may be composed of the following ingredients in the proportions indicated: Y

Waterv '-ounces-; 160 Ammonium carbonate ..-do 31/2 Orange shellac pound-- 1 Ammonium bichromate--..- grains 360 The coating must be uniform and of substantial thickness. To produce this, the liquid composition is applied while the copper sheet is mounted on a spinner rotating in a horizontal plane and while warm air is directed against the face of the sheet to dry the composition. A plurality Vof'coats of the enamel are usually required, each one being dried before the subsequent coat is applied. The coated sheet is then cut into smaller rectangles of sizes convenient for handling and with a view to producing a maximum numberr of reticles on each metal blank.

' For use in contact printing of the outlines and designs for a group of reticles, suitable transparent negatives are prepared photographically from accurate. line drawings 'in accordance-with procedure which is well known in the art. Duplicate negatives are superimposed one on the other with the reticle outlines and designs of the respective negatives in registry with each other. These superimposed negatives are then fastened together along opposite margins to form an envelope for one of the metal blanks. A typical arrangement of the negatives and blanks is illustrated in Figs. 5 and 6 ofthe drawing wherein negatives I6 and I1 are shown superimposed one on the other with the outlines and designs for four reticles in reg-- istry with each other. Adhesive strips I8 extend along the ends of the negatives to fastenl them together, leaving an opening along a longitudinal margin to admit a metal blank 2I between the The lines on the negatives representby the numerals' I9 and the interior designs, which must be accurately located Vwith respect to the images i vidual reticles in soluble condition. The lines are periphery, are indicated by the numerals 20. To temporarily fasten the blank 2| within the envelope formed by the negatives, in proper relation to the several designs, suitable adhesive tape members 22 may be employed. 'Ihese are aixed to the outer face of the negative I1 over triangular openings 23 formed therein so that the inner, adhesive coated surfaces of the members 22 make Contact with the metal blank to hold it in iixed relationship to the negatives. With a 4'5 ampere lamp at a distance of 35 to 36 inches, exposure of the negatives for from two to four minutes Yhas been found to be suiicient in most cases.

Such exposure renders the exposed area of the cold top enamel insoluble to the developing solution which is subsequently applied but leaves the of the designs and outlines of the indithen developed by thorough washing in a solution 4such as the following in the proportions indicated: i; Denatured alcohol (Formuia #5) gaucns-- 5 Malachite, green grains-- 20D Distilled water ounces-- 32 This is applied until the lines appear sharp and clean on the blank which is then washed in water and dried. The lines are now ready for etching into the metal.

AIt will be evident that the selection of the reagent for etching is dependent on the character of the material comprising the blank. Where the latter is made of copper, the operator may apply aprotective coating of asphaltum or other resist to the edges and one face of the blank and a number of the blanks may be temporarily attached to a supporting plate of glass or other suitable material using the asphaltum as an adhesive and leaving one face of the blanks exposed for the rst etching treatment. The Work is now placed in an etching machine wherein ferrie chloride is used to etch the lines to a predetermined, uniform depth and to dene the width of the lines on the exposed, enamel-coated face. Fig. 7 of the drawing illustrates a fragmentary part of the assembly of the work on a glass plate 24 and with the thickness of the various materials greatly enlarged for clearness, but notnecessarily to scale. As here shown, a fragment of the metal blank 2| has the cold top enamel coating 25 on both faces and the asphaltic masking material 26 covers one face and constitutes an adhesive for securing the blank to the plate 24. One of the linesv 28 is shown as having been etched part way into the blank 2| while one of the photo-printed lines 2l on the opposite face of the blank is shown in registry with the partially etched line.

Use of ferrlc chloride of 40 degrees Baume test for a period of 2 to 5 minutes is usually sufficient to cause the lines to penetrate the desired depth into the metal. By careful control of the time, both the width and depth of penetration is regulated to give any desired width of line. For flat reticles, such as'those shown in Figs. 1 and 2, the etching from one face is extended approximately half way through the metal blank and then the blank is reversed on the supporting plate, the asphaltic masking material is removed from the outer, unetched face and then the lines on this face are etched until the complete transparent design and the circles dening the peripheries of the individual blanks are caused to completely penetrate the. metal. In some cases the final nishing to insure uniformity in the width of lines is carried out manually by the use of a line brush and the etching; solution. The re- Sultinewqltlis .mantendra VLele amine-1selution suchn washing inA acau'stijc solutionfollowedby a' Water bath.: Where vnon-reflecting surfaces areV required," theblanks gare" oxidized 'byf immersionY in suitablesulphur compound'which' is also washed off'afterfajshortperiod ofimrnersionz bef retainedintaw unnr the etchingL from the secondfa'ce of"each'has 'been completed.I This greatly facilitates the. handlingof a largenumber o f theV` rel'licles.v Since 'the outerpripheries'of 'the individual' reticles are ".forxned'lcry the etching procedure simultaneously with the' 'etching ofA the'transparentilines ojf theinterior design. We insurenotA only 'the accurate sizing of the blanks butalso the ac curatelocation or centering or the transparent lines respectto'the periphery;

Our procedure formakingthe' concave-convex or dishshaped' reticl'esj; exemplifiedi'by the `one' 'i1-v lustrated in Figs; Sanddj is'like thathereinbe'- fore described reference "to vtheI flatreticles up toM and including the mounting ofv the Aflatv blanks on the-supportingfplate preparatoryV` toY etching.- To proceed'-fromethis-*pointg'we etch the design and 'outline `of theseveralfreticles onablankpa-rt *Way -i-nto oneface: Theiine line design is `preferably` caused to penetrate `to-adepth ofy about one-thirdof.Y thethickness o-f the blank and then masking material isd applied-to the design andfthisis 4followed 'by-.etchingiof the outlines or: peripheries or the several f reticles.- completely through the metal thus forming individualat blanks. These blanksV are. then. removed from thesuppnrting.- plateiandiare;severally:.shaped .to o thedesiredicuryatnrensinga.simplepress hav- Thl ysug'zceeding step. in .the operation is illustrated in Fig. 8 wherein .the d ishshaped blank 29 is vshovvn .with its. enamel coating V-Sil and with the partially etched lines 3l located at the concave face. As further illustrated, the blank is attache@ to a Supporting platen. of. glass or other translucent material usinga fillingof translucent Wax 33 between the concaveface of the blank and plateand Withsultable masking material 34 to protectthe periphery ofthe blank from the, etching`A solution which issubsequently applied. The assembly including ther blank, together with others similarly mountedonthe plate 32', is next placed in the ,etching machine Where the openings 35 representing the` design in the enamel coating at Vthe convexfaceof the blank .allow the etching to proceed completely through the blank. The etching is. continued .until the designs appear clear-cut and transparent. The end point may be readilyl determined "by inspection where the. support 32 as Well Las the waxv masking materialj33 are translucent. With alight beneath the plate 32 the. operatorinspects the vtransparent lines'by observation througha magnifying glass. at the opposite or convex faceV ofv the blank. Without removing theV several'reticles from the glass support slight irregularities in the lines may be corrected'by the. use of a sharp instrumentor by'manual, etchingas required. The final cleaning operation andx` where, required, the

oxidationoff the` surfacesfmay be accomplished Y.

as described with reference'to the'fiat'reticles.

By 4-constructingeoursfreticlesefiom*sheet-metal.

of uniform thicknessthroughoutfandonly thi-ck@- enough to constituteaseltfsustainingfunit;n `we the further advantage of' minimizingwthe time required foretching and 'amount' offfetching solution used in theprocess. We -alsoreducelthe cost of manufacture by our useio'f fdu-plioatefnegatives. to photo-'printv both 1 faces -of fai rlarge-'number of blanks simultaneously andbyf-using lthe-flat negatives for printing both* fthe' plane and'ciisllfsl'iapedv reticles,r including'reticleoutlines`l By die-shaping the concavo-convex-bianksvafter 1 'the design has been etchedfonfthe concave yface and by sub-y sequentlyr :completingffthefetching from lthe convex face, thev procedure*ise-simplifled'without losing, the: lines 'and accurate lcontrol ofthe width of otherv dimensfons'of `V`'the design or ycausing distri-- mental distortion during `'the shaping.

Where the linesv areto loe-formed by vetching procedure as hereinbefore described, aapractical upper limit forfthe `thickness uo'ftr'ie metal blanksis equal tofapproinmatelyfgog off an inch since irregular Vlinesresulti' it is' attempted to etch lines from either faceA toa depthgreaterl tha-n about lAODths of anunch'. The' lower `lmitoi thickness of metal ls'idep'endentjonthediameter ofthe reti'cles .and .condition whereitilsto'be used, but experience indicates'thatiwitii presently available and' suitable metals; thicknesszof'less than 2/000 of'aninchwouldrender the devicesiinsufliciently rigid tov be selfesustainngjunderordinaryy conditions ofrluse.

The reticle/shownv in Figs. :9 and 10 comprises a metal disk 3`ll lWlfi'clfi's. substantially thicker and more rigid` than. those shown in Figs.v 1 to 4,y inclusive. A diskapproxmatelyan eighth of an inch thick, for example, may beused. A fine, transparent network .oflnes or designs, indicated generally by the.nunieral31",'l is. cutltliroughy the metal ofthe disk and: ln some cases other neline perforations, suchasfthe legend`38'; may also be out through the disk accordngto our invention. The thickness of fthe material 35i-immediately adjacent tothe legend.y and design is`,greatly reduced being preferablyV from 34000 t0A oo of an inch ,in thickness.

The reticle shownin Figs. 11 and 12j comprises a nrietalrbodyMloi dish shape havingthe inner and outer faceswhich are respectively concavely and convexly spherical; onof other. desired shape. A ne line design 4l consisting of radially extending and arcuate, concentric lines, .extends through a central 'portion 42 of the body 49 which is reduced to the ydesiredthickness of 'from /iooc to 2/100of an inch. In addition to the several fine. lines of design 4|, the body 40 has-a minute central perforation 43. The segments of the central portion 42 are connected togetherby filaments of metal along' opposite sides ofy the radial lines shown.

Our procedure to'fo'rin the fine lines, ,perforations or other design onthe selected'areas of the thicker metal'blanks Willbe .understood from the following detailed description.V The. blank is ordinarily die cutrfrom sheet orplatevrnetal to the desired size and Whererequired is shaped by suitable forming andfstamplngoperatons followed by buiing to produce smooth faces., These are then burnished with a-fineabrasiveto give fine toothed surfaces. At least; one .ofithesesurfaces is then rendered light sensitive. b'yfapplying ia. solution .of

either cold top or hot top enamel,- as hereinbefore 7 described, each coat of the solution being dried before the subsequent coat is applied.

Subsequently the required design is projected on the sensitized coatingthus formed on the blank by the use of a transparent negative. For this purpose a photograph-of a drawing of the desired design may be preparedV in such manner that a silver emulsion capable of being fstripped or transferred to `a. previously prepared negative sup.. port is produced according to conventional practice. For accuracy the negative must be shaped to t the metal blank before the silver emulsion is transferred to it. As the negative support, a disk of transparent Celluloid or other suitable plastic material may be used. After heating the plastic disk to soften it. itis placed under pressure between two of the stamped out metal blanks with which it is to be used and is allowed to set in this shape. To a face of this support the design in the form of a silver emulsion transfer is stripped to complete the negative.

After this negative has dried it is held in contact with the sensitized coating of the metal blank in a suitable vacuum frame. Firm, uniform contact is thus maintained between the negative and the light sensitive coating on the metal blank while the design is reproduced'on the coating by exposure of the negative and blank under an arc lamp of suitable power. With a 45ampere lamp at a distance of thirty-five to thirty-six inches, exposure of the negative for from two to four minutes has been found to be sufficient. Such expo-sure renders the exposed area of the cold top enamel insoluble to the developing solution which is subsequently applied, but leaves the image of the design in a soluble condition. The fine line design is then developed by applying a solvent such as that described with reference to the thinner blanks. This is applied until the image appears sharp and clean on the blank which is then washed in water and dried. The image is now ready for etching into the metal.

Where the blank is made of copper, a protective coating of asphaltum or other resist is next applied to the edges and back face of the blank which have not previously been covered with the enamel, leaving the design open for etching. The work is then placed in an etching machine and etched with a suitable reagent. The etching is thus caused to penetrate the surface of the metal to a depth of from 2/iooa to 1/wo of an inch. It has been found that the required accuracy, uniformity and iineness of line cannot be obtained if the etching is allowed to penetrate the metal to a greater depth.

Fig. 13 of the drawing illustrates the blank 36 with the design 3l etched into the metal face with its enamel coat ,44, the back face of the blank having the asphaltum coating 44a. Proceeding with the etched blank, the lines are lled with a protecting paint or mastic 45, such as asphaltum, and the asphaltum or other resist is removed from the :back of the blank as shown in Fig. 14. Now the thickness of the blank directly back of the design is reduced, preferably by etching procedure. With a copper blank ferrie chloride of .the same grade as that used in etching the desi-gn on the front of the blank may be used on the back face. The etching from the back is carried to the point where the bla-ck of the asphaltum filling 45 begins to show through. Using a fine brush, the operator may manually complete the operation by applying -ferric chloride until all of the lines appear uniformly and sharp in black. The recess formed-by etching from the back is indicated by the nuof the etching, or from 2/iouo to l/ioo of an inch thick. Finally the' blank is placed in a cleaning solution adapted to dissolve the asphaltum filling for the design as well as the other staging material or enamel. By holding this inished reticle to the light the entire design appears fully open and sharp.

Where extremely fine and perfectly clear cut lines are not required and where the thickness of metal need not exceed .01 inch, our process may be carried out entirely from one face of the blank, the design being photo-printed thereon,

developed and then etched while the other face of the blank is merely masked. Thus the transparent designs may be formed in a number of blanks in one etching operation and without removing them from a common support.

To increase the illumination of the image it is sometimes desirable to form a highly light-reflecting surface on the face which is to be exposed to artificial light. This may be accomplished by coating or plating on a white metal, such as silver, after the design has been etched through and while protecting the lines or perforations by the use of a filling of suitable masking material. For example, electro-plating with silver in this manner gives the desired reiiecting surface without detracting from the clarity of the design.

The presentv application is a continuation in part of our abandoned application Serial No. 460,822, filed October 5, 1942, for Reticle and process for making the same, and is a division of our abandoned application Serial No. 497,486, filed August 5, 1943.

We claim:

1. A reticle comprising, a unitary body of metal formed with ne, sharp, elongated perforations not exceeding .01 inch in width, dening a lightpervious design on an opaque field, the thickness of said body over the area of said design not exceeding .02 inch and selected perforations being separated by minute reinforcing filaments of metal, the filaments being integral with the body, 2. A reticle comprising, a unitary metal body of self-sustaining thickness formed with line, sharp, arcuate perforations defining separate segments of a circular, light-pervlous design on an opaque held the ends of said segments being separated by minute filaments of metal, the filaments being integral with the body, whereby the central portion of the body is supported.

3. A reticle comprising, a unitary metal disk o'f self-sustaining thickness having fine, sharp, arcuate perforatons not exceeding .01 inch in width, defining separate segments of a circular, light-pervious design disposed concentrlcally to the periphery of the disk, the ends of the several segments being separated by minute filaments of metal supporting the central portion of the disk. 4. A reticle comprising, a unitary metal body having a thin central portion not exceeding .02 inch in thickness and. a relatively thick, integral peripheralV portion, the Vrelatively thin central portion being formed with fine, elongated perforations not exceeding .01 inch in width. defining a light-pervious design on an opaque iield.

Y 5. A reticle comprising, a unitary metal body of concavo-convex shape formed with ne, sharp perforations not exceeding '.Olinch in width, de-

' 9 10 ning a light-pervious design on an opaque eld.

6. A reticie comprising, a unitary metal body REFERENCES CITED of self-sustaining thickness and concave-convex The following references are of record in the shape formed With fine, sharp, arcuate peri'orame of this patent; tions not exceeding .01 inchin width, dening 5 separate segments of a circular, light-pervious UNITED STATES PATENTS design on an opaque eld, said design being in- Number Name Date terrupted by minute filaments of metal support- 378,423 Baynes Feb. 28, 1888 ing the central portion of the body.` 1,380,333 Rosales May 31, 1921 10 1,958,456 Warrens May 15, 1934 NORMAN B. MEARS. 2,177,094 Carter Oct. 24, 1939 HARVEY T. HOLSAPPLE. 2,339,723 Russell Jan. 18, 1944 

